Bone-Mounted Robotic Surgery
U.S. Pat. No. 6,837,892 of one of the present inventors, discloses a miniature surgical robot and a method for using it. The miniature surgical robot attaches directly with the bone of a patient. Two-dimensional X-ray images of the robot or a target on the robot base, on the bone are registered with three-dimensional images of the bone. This locates the robot precisely on the bone of the patient. The robot is then directed to pre-operative determined positions based on a pre-operative plan by the surgeon. The robot then moves to the requested surgical site and aligns a sleeve through which the surgeon can insert a surgical tool.
FIGS. 1-4 and 6-8 are prior-art figures that are all taken from U.S. Pat. No. 6,837,892
FIGS. 1A-1B illustrates an image guided, robot assisted, surgical system. Included in this system generally, as shown in FIGS. 1A-1B, is a bone attached surgical robot 30; a control unit 10 that matches data from CT scans and C-arm images to locate robot 30 on the patient's bone and directs the robot according to pre or intra-operative plan Control unit 10 generally includes a CPU and user interface communicating with display 20 and robot 30.
As an example of bone-mounted surgical robot see FIG. 2 where a robot, 30, directs a sleeve, 60, along a pre-planned trajectory through which the surgeon insert the surgical tools.
Clamp 40 (illustrated in FIG. 2) is an example of one embodiment according to the invention by which a robot may be attached to a bone for assisting in a surgical procedure. Other attachment devices can also be incorporated with a robot such as, for example, K-wire connections. FIG. 8 illustrates such a K-wire connection. K-wires 950 are inserted into the bone by standard surgical procedures. Robot base 35 contains an elongated slot through which K-wires 950 are inserted. Screw 960 can then be turned and tighten pinch plate 970 against robot base 35 pinching K-wires 950 between pinch plate 970 and robot base 35 holding robot 30 tight with respect to K-wires 950 and bone 50.
FIG. 5 is a close-up of sleeve 60 and surgical instrument 70 deployed therein. The guide sleeve 60 is firmly held by the robot arm 72 in its predetermined pose, such that the surgical drill 70 enters the bone 75 at the desired location and the desired angle determined by the robot pose. If the drill 70 enters the bone at approximately normal incidence, there is little tendency for it to skive. On the other hand, if the surgical plan requires that the drill enters the bone at a non-normal incidence, as shown in FIG. 5, and which may commonly occur in spinal surgery because of the topographical nature of the surface of the vertebrae, there is a tendency for the drill to skive away 76 from the point of entry 77. Since the robot generally holds the sleeve firmly, the drill trajectory itself will not usually change, but when the lateral component of thrust resulting from the non-normal entry angle becomes larger than a certain level, this may cause the bone to move or flex away from the drill center line, thus resulting in an inaccurately positioned bore. The stability of the robot mount to which arm 72 is ultimately attached, may also contribute to the loss of accuracy due to the skiving effect. Some embodiments of the present invention are useful for overcoming this situation.
FIGS. 9A-9B are schematic drawing of the element in FIG. 5 including sleeve 60 having sleeve axis 62. Also illustrated in FIGS. 9A-9C is surgical instrument 70 having instrument axis 72 which (i) is an elongate axis of the surgical instrument 70 and/or (ii) an axis defined by and co-linear with an “operation direction” 74 of the surgical instrument—i.e. a direction at which the surgical instrument operates—e.g. a drilling direction in the case of a drill. As shown in FIG. 9C (side view), surgical instrument 70 may be snugly disposed within sleeve 60 so that operation direction 74 and/or a direction of axis 72 is determined by a direction of the sleeve 60 (i.e. defined as the direction of sleeve axis 62). As shown in FIG. 9C, the surgical instrument 70 is aligned with sleeve 60—i.e. so that sleeve axis 62 and the instrument axis 72 of surgical instrument 70 are aligned with each other.
FIG. 9D is a top view the system of FIG. 9C illustrating the annular region 68 between the instrument 70 and sleeve 60—since the instrument is ‘snugly’ disposed within sleeve 60, this annular region is relatively thin—i.e. the tolerances are tight.
As illustrated in FIGS. 10-11, in some embodiments, there is an inner sleeve 160 having sleeve axis 162 that is disposed within outer sleeve 60—for example, snugly disposed therein so that respective axes 62, 162 are aligned. FIG. 11B illustrates a top view including annular regions 88 and 98.
One example of an inner sleeve is a surgical canulla 160—for example, as illustrated in FIG. 12 including knurled knob 120 at a proximal end, and a tapered distal end 130.
Skiving
When drilling into a bone, skiving may occur when the drilling instrument is not directed perpendicular to the bony surface—the instrument may skive or skip across the bony surface. Skiving is not limited to surgical drills. In another example, when a canulla device in contact with a bone slips along the surface of the bone, this also may be referred to as skiving.
A number of prior art patent documents disclose methods apparatus and methods for minimizing (or mitigating) a risk of skiving or an extent of skiving. This may occur by stabilizing an instrument upon the surface of the bone or by reducing the imparting of a skiving force from the instrument upon a surface of the bone. Examples of patent documents that disclose apparatus or methods for reducing skiving include WO2011014677 and U.S. Pat. No. 8,469,963 (of one of the present inventors).